Attachment for door locks and latches



April 14, 1931. F. c. RUSH ATTACHMENT FOR DOOR LOCKS AND LATCHES F'i led May 27, 1929 ATTORNEY-8' Patented Apr. 14, 1931 FRANCIS C. RUSH, OF DETROIT, MICHIGAN ATTACHMENT FOR DOOR LOCKS AND LATCHES Application filed May 27, 1929. Serial No. 366,322.

This-invention relates generally to looks and latches and refers more particularly to an attachment for latch bolts thereof.

. Heretoforeit has been possible for un- 5 authorized persons to pick locks and latches by inserting a suitable tool or instrument such as a knife blade between the free edge of the closure and its jamb into engagement with the usual bevelled or inclined face of 10 the latch bolt and thereby force the latter rearwardly to retracted position.

With the present invention, however, the latch bolt cannot be retracted by any unauthorized person in such a manner due 15 primarily to the provision in the bolt of a spring pressed plunger which is normally in the plane of the bolt but is adapted to be projected by the tool or instrument into engagement with a portion of the latch casing to prevent the latch bolt from being retracted.

In the accompanying drawing:

Figure 1 is a sectional view through a door and jamb and showing an attachment gmbodying my invention applied to the latch olt;

Figure 2 is an enlarged fragmentary perspective view of the latch bolt and attachment;

9 Figure 3 is a sectional View taken on the line 3-3 of Figure 1;

Figure 4 is a detail perspective view of the plunger.

Referring now to the drawing, 1 is a door, 2 is a latch casing carried by the door at the free edge thereof, 3 is a reciprocating latch bolt normally projecting through a wall elof the casing, 5 is a jamb, and 6 is a keeper or striker plate on the jamb adapted to be engaged by the bolt 3 when the door is in closed position.

To prevent the bolt 3 from being forced rearwardly by a tool such as 7 While the door is closed, I have provided a spring pressed plunger 8 movable transversely of the bolt 3. As shown, this plunger is U-shape in form and straddles the bolt. Preferably the base 9 of the Uis relatively wide and is received in a suitable slot 10 in the bevelled to face 11 of the bolt, while the arms 12 and cost. Moreover, the base 9 13 of the U are received in slots 14 and 15 in opposite edges of the bolt and have inturned end portions 16 and 17 that are normally in recesses 18 and 19 in the rear face of the bolt. As illustrated in Figure 1, a coil spring 20 is in a recess 21 in the bolt in rear of the base 9 and normally holds the inturned arm portions 16 and 17 in the recesses 18 and 19 and holds the base 9 in line with the beveled face 11. Preferably this base 9 is inclined at substantially an obtuse angle to the arms 12 and 13 so that it conforms in inclination to and constitutes a continuation of the bevelled face 11 when the plunger is in neutral or normal position. If, however, a tool such as 7 is inserted between the jamb 5 and the door 1 to pick the lock, the point 7 of the tool will engage the base 9 of the plunger and will push the latter transversely of the bolt so that the inturned arm portions 16 and 17 will extend over and constitute shoulders or abutments upon the wall 4 of the casing. As a result the bolt 3 remains motionless and can not be wedged or forced by such a tool rearwardly to retracted position.

Thus from the foregoing it will be apparent that the plunger 8 will effectively pre vent locks and latches from being picked.

Such a plunger is simple in construction and can be manufactured at a comparatively low so in addition to serving as a continuation of the bevelled face 11 of thebolt is relatively wide so that the surface to be engaged by the instrument or, tool is of sufiicient size to insure proper engagement therewith. The inturned portions 16 and 17 of the arms also serve a dual function; first, to engage the bolt and limit outward movement of the plunger; and second, to extend over the latch casing and prevent 9o retraction of the bolt when the plunger is moved inwardly by the tool. In practise the depth of the recesses 14 and 15 is substantially equalto the thickness of the arms 12 and 13, and the depth of the recesses 18 and 19 is substantially equal to the thickness of. the inturned portions 16 and 17 so that the arms 12 and 13 and inturned portions 16 and 17 will normally be flush with the adjacent surfaces of the latch bolt. Such plungers may 1H0 

